The present invention concerns the field of multiflow, in particular double-flow, jet engines and more generally that of turbomachines.
A double-flow jet engine comprises a gas turbine engine through which flows a flow of gas referred to as the primary flow driving a fan delivering a flow of air referred to as the secondary flow. When the fan is placed at the front of the engine, it discharges aspirated air that is separated into two concentric flows: one the primary flow, the other the secondary flow. The air of the primary flow is compressed again and then mixed with fuel in a combustion chamber to produce a high-energy gas flow that drives the downstream turbines. One of the turbines is connected by a shaft to the fan rotor, which it drives. The secondary flow in civil aircraft engines provides most of the thrust of the engine and the fan is consequently of very large diameter.
The fan rotor comprises a wheel the hub of which is fastened to the drive shaft and the rim of which comprises substantially axially oriented cells. The axial direction is that of the engine shaft. The blades have their root engaged in the individual cells, and form the fan rotor. A fan blade comprises a root, an airfoil of aerodynamic profile and a root shank between the root and the blade. To constitute the boundary surface between the rim of the rotor and the airstream and to ensure continuity of the primary flow, platforms are interleaved between the blades. Differing from the higher compression stages and because of the large dimensions of the blades, the platforms of the fan rotor are separate parts rather than integral with the blades. Note that the inside radius of the airstream increases significantly between the inlet and the outlet of the fan rotor.
Clearance is provided between the platforms and the blades to allow limited relative movement of the blades during the various phases of operation of the engine. This clearance is plugged by an elastomer material seal fixed along the lateral edges of the platform and bearing against the adjacent blade.